Lower back pain is a serious problem in this country. It is estimated that eight out of ten Americans at one time or another will suffer from severe back pain. Most lower back pain from sitting is related to poor posture in which the person sits in a slumped or rounded posture. This poor posture occurs more readily when the seat or chair does not give proper support.
The position that we hold our spine when we sit is crucial to preventing or exacerbating back problems. The proper position is for the spine to be held in a forward curve called a lordosis. When a proper lordosis is maintained, there is less pressure on the lower back. This can be illustrated with regard to the lumbosacral angle, or Ferguson's angle, formed at the base of the spine. See Yochum, T. R. and Rowe, L. J., Essentials of Skeletal Radiology, Vol. 1, Williams & Wilkins, p.189 (1987). When the person is upright, the normal lumbosacral angle is 41°, with a standard deviation of ±7°. A decrease in the lumbosacral angle, such as when the lower back is becomes rounded when a person is seated in a slouched position, has been implicated as a mechanical factor in producing lower back pain by increasing disc pressure and placing undue stress on the lumbosacral posterior joints. Providing proper lower back support while seated would maintain the lumbosacral angle within its normal limits and thus alleviate lower back pain.
Numerous innovations for lower back supports have been known, such as spinal column supports having cushion material such as gaseous fluid or liquid fluid. Lower back cushions also exist in a variety of sizes, but are not adjustable and are generally inadequately designed to reduce the lumbosacral angle. Back supports which circumferentially enclose the body and the spine, in the form of a belt, are also known in the art. These devices are in the form of a back brace or support, most of which create compression around the waist and back to squeeze the spine, giving it support.
For example, prior art references provide back support means by which the supported area at the small of the back can be changed in a manner to effect varying degrees of support without having to change the construction of the pads or cushion. Romano, U.S. Pat. No. 4,135,503, discloses an orthopedic device which provides ambulatory traction to specific levels of the spine using an inflatable bladder. The bladder is affixed between a rigid base plate and an apertured template plate so as to extend outwardly from the base plate and inwardly toward the spine to create compression against a predetermined portion of the back and spine. The plates are mounted to a belt as well as brace strapping which is relatively unyielding when placed around the patient.
Eichler, U.S. Pat. No. 4,245,628, discloses a corset-like, back support bandage having a support pad with a fastening plate and an arch rib plate to which there is mounted an intermediate foam cushion. Racz et al., U.S. Pat. No. 4,552,135, discloses a belt for supporting the lower spinal column having a centrally located chamber in the rear of the belt filled with a sponge-like material. A valve connects the chamber with the atmosphere such that when the rear of belt is compressed, air is forced out. When the compression force on the chamber is removed, the sponge-like material forces the chamber walls apart, causing air to flow back into the chamber.
In contrast to the above-cited art, the present invention provides a back support especially suited for supporting the lower spinal column at the small of the back in a proper lordosis by employing a variably inflatable bladder or cushion of novel design arranged centrally respective to the small of the back. The cushion is configured and dimensioned to provide variable pressure and support to the L3, 4 and 5 vertebrae and the surrounding para-lumbar musculature when inflated. The cushion pushes against the back of a seat which in turn creates a counter pressure to the back. The novel, hemi-elliptical shape of the cushion results in the majority of the cushion being extended into the center of the spine while the outer portion pushes against the para-lumbar musculature of the lower spine and provides support across both sacro-iliac joints. The cushion is held into optimum position by a circumferentially extending belt which positions and holds the cushion within the small of the back. The size of the cushion and the air pressure within the cushion can be variably adjusted by the use of a manually operated air pump.